Agnes Martin's Night Sea (1963) is a large canvas of hand-drawn rectangular grids painted in luminous blue and gold. In this illustrated study, Suzanne Hudson presents the painting as the work of an artist who was also a thinker, poet, and writer for whom self-presentation was a necessary part of making her works public. With Night Sea, Hudson argues, Martin (1912--2004) created a shimmering realization of control and loss that stands alone within her suite of classic grid paintings as an exemplary and exceptional achievement. Hudson offers a close examination of Night Sea and its position within Martin's long and prolific career, during which the artist destroyed many works as she sought forms of perfection within self-imposed restrictions of color and line. For Hudson, Night Sea stands as the last of Martin's process-based works before she turned from oil to acrylic and sought to express emotions of lightness and purity unburdened by evidence of human struggle. Drawing from a range of archival records, Hudson attempts to draw together the facts surrounding the work, which were at times obfuscated by the artist's desire for privacy.Critical responses of the time give a sense of the impact of the work and that which followed it. Texts by peers including Lenore Tawney, Donald Judd, and Lucy Lippard are presented alongside interviews with a number of Martin's friends and keepers of estates, such as the publisher Ronald Feldman and Kathleen Mangan of the Lenore Tawney archive, which holds correspondence between Martin and Tawney.